1. Field of the Invention
The present invention relates to a starting system for large internal combustion engines, for example, large natural gas fueled engines, provided with associated air compressors and in-head air starting valves.
2. Description of Related Art
It is known in the art to provide starting systems for multi-cylinder internal combustion engines, for example, those located at remote locations, by use of compressed air stored at the site of the internal combustion engine. The compressed air may be restored when the internal combustion engine is running by a compressor driven by the engine. These systems direct the compressed air to one or more cylinders of the engine at the proper crank angle and in the proper order to drive rotation of the engine crankshaft to a start-up speed.
Some prior art systems are entirely mechanical and comprise a compressed air distributor that is driven by the camshaft. A rotating distributor disk directs compressed air to conduits connected to valves in the head of each driven cylinder. One example of a mechanical starting system is disclosed in U.S. Pat. No. 3,722,210 entitled “Rotary Pneumatic Starter Distributor for Internal Combustion Engine.” The mechanical starting systems have been implemented to provide advance of timing of the compressed air directed to each cylinder with increase in speed by mechanical rotation of the distributor. The advance results in more economical use of starting air and helps to achieve start-up speed.
Other prior art systems make use of magnetically driven (solenoid) servo valves at the head of a plurality of cylinders. In U.S. Pat. No. 4,324,212 entitled “Compressed Air Starter,” a capacitive transmitter rotated in relation to the rotation of the crank shaft generates a signal during a portion of the angle after top dead center (TDC) for opening a solenoid-driven servo valve. With use of an electric distributor, only one capacitive transmitter is required. However, the advance angle (angle after TDC at which the solenoid valve opening is initiated) and duration angle (crank angle through which the valve is held open) are fixed, which is a significant drawback.